The 3 Gb switch in windows still allows only 2 Gb of RAM maximum for one program. The other gig is useful because it keeps windows stable and running in the background. I have run both Algor and CFDesign with the switch and seen a greater ability to multitask but no more calculating power. Linux will allocate as much RAM as a program will consume so the pressure is on the Fluent software to properly allocate that much RAM. A good source for more information on this are the people at CFD++. They have great software and understand both operating systems well.